This invention relates generally to braze joining of metallic components and more particularly to braze alloy preforms.
Metallic components, especially gas turbine engine components, are often bonded to each other through brazing. In brazing, a metallic alloy with a melting point lower than the components being joined is placed between the components. The entire assembly is then heated to a temperature above the melting point of the braze alloy and below the melting point of the components, causing the alloy to flow into the joint. When cooled, the result is a structural joint that is produced without detrimentally effecting the metallurgical properties of the joined components.
Several prior art methods exist for placement of the braze alloy into the joint. But there are shortcomings associated with each prior art method. For example, braze slurry can used, but the material is hand applied and the control of the alloy bead size is operator dependent. Braze rope can be produced from powders and binders but it has a very limited shelf life and is fragile to handle. Braze wire preforms can be produced by drawing wire, forming the shape and then boronizing the wire to introduce melting point depressants. However, only alloys that are drawable or contain boron can be produced by this method. Preforms can be produced by casting a tape of braze material and then sintering the tape. The preform shapes are then cut from the sintered tape. This process limits itself to two-dimensional shapes. Three-dimensional preforms can be produced but this requires additional hand benching or machining.
Accordingly, there is a need for a method of producing durable braze preforms having arbitrary shapes.